/* OBS.
 * a -> prietenul a vine la party
 * a + n -> prietenul a nu vine la party
 * 
 */
#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
using VI = vector<int>;
using VB = vector<bool>;
using VVI = vector<VI>;

ifstream fin("party.in");
ofstream fout("party.out");

int n, m;
int idx, total;
VI index, low, id;
VB in_stack;
VVI G;
stack<int> stk;

void ReadInput();
void Solve();
void DFS(int node);
void ExtractCTC(int node);

int main()
{
	ReadInput();
	Solve();
	
	return 0;
}

void Solve()
{
	for (int node = 1; node <= 2 * n; ++node)
		if (!index[node])
			DFS(node);
	
	VI ans;
			
	for (int node = 1; node <= n; ++node)
		if (id[node] == id[node + n])
		{
			fout << 0;
			return;
		}
		else if (id[node] < id[node + n])
			ans.push_back(node);
			
	fout << ans.size() << '\n';
	for (int node : ans)
		fout << node << '\n';
}

void DFS(int node)
{
	index[node] = low[node] = ++idx;
	stk.push(node);
	in_stack[node] = true;
	
	for (int nbr : G[node])
		if (!index[nbr])
		{
			DFS(nbr);
			low[node] = min(low[node], low[nbr]);	
		}
		else if (in_stack[nbr])
			low[node] = min(low[node], index[nbr]);
		
	if (index[node] == low[node])
		ExtractCTC(node);
}

void ExtractCTC(int node)
{
	total++;
	int next;
	while (!stk.empty())
	{
		next = stk.top();
		stk.pop();
		
		in_stack[next] = false;
		id[next] = total;
		
		if (next == node)
			break;
	}
}

void ReadInput()
{
	fin >> n >> m;
	
	index = low = id = VI(2 * n + 1);
	in_stack = VB(2 * n + 1);
	G = VVI(2 * n + 1);
	
	int u, v, type;
	while (m--)
	{
		fin >> u >> v >> type;
		
		cout << u << ' ' << v << ' ' << u + n << ' ' << u + v << '\n';
		
		if (type == 0)
		{
			G[u + n].push_back(v);
			G[v + n].push_back(u);
		}
		else if (type == 1)
		{
			G[u + n].push_back(v + n);
			G[v].push_back(u);
		}
		else if (type == 2)
		{
			G[v + n].push_back(u + n);
			G[u].push_back(v);
		}
		else
		{
			G[u].push_back(v + n);
			G[v].push_back(u + n);
		}
	}
}